Bioengineering of Fungal Biomass for Bioethanol Production: Recent Progress and Challenges

Bioethanol utilization is a global move toward the production of renewable energy and the lessening of fossil fuel dependence. In this chapter, we summarize progress in the nutritional bioengineering of fungal biomass and the corresponding challenges that must be mitigated for industrial bioengineering of fungal biomass to be implemented at a global scale. Targeted genetic modifications, specifically to metabolic pathways of fungi, have been the focus of the last 10 years of research. The use of Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)-Cas, RNAi, and transcriptional engineering has helped to understand and improve traits such as carbohydrate storage, stress tolerance, and substrate utilization effectiveness. Solid-state fermentation and consolidated bioprocessing technologies are very promising and even more so in combination, since they integrate multiple fermentation steps, lowering the energy input plus the demand for exogenous enzymes. The combination of the physicochemical factors and legislative constraints to field release of genetically altered fungi has a long and complex history, especially in countries with more stringent biosafety legislation. Priorities in advancement will include developing strong fungal chassis that can withstand industrial stressors, enhance pentose transport systems, and eliminate expensive pretreatment requirements. The use of synthetic biology, adaptive and computational modeling will be crucial in engineering advanced strains of microorganisms for commercial bioethanol production.